From f1b2f2020afe8373dd38deca996092896d1970e2 Mon Sep 17 00:00:00 2001
From: Jiachi Liu <inbox@huozhi.im>
Date: Tue, 29 Jul 2025 13:01:35 +0200
Subject: [PATCH] [segment explorer] normalize path when running inside
 monorepo

---
 packages/next/src/server/app-render/app-render.tsx   |  6 +++---
 .../src/server/app-render/create-component-tree.tsx  | 12 ++++++------
 .../src/server/app-render/segment-explorer-path.ts   |  8 +++++++-
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/packages/next/src/server/app-render/app-render.tsx b/packages/next/src/server/app-render/app-render.tsx
index d8c90e1ea249..85f616ae5556 100644
--- a/packages/next/src/server/app-render/app-render.tsx
+++ b/packages/next/src/server/app-render/app-render.tsx
@@ -4201,9 +4201,9 @@ const getGlobalErrorStyles = async (
   }
   if (ctx.renderOpts.dev) {
     const dir =
-      process.env.NEXT_RUNTIME === 'edge'
-        ? process.env.__NEXT_EDGE_PROJECT_DIR!
-        : ctx.renderOpts.dir || ''
+      (process.env.NEXT_RUNTIME === 'edge'
+        ? process.env.__NEXT_EDGE_PROJECT_DIR
+        : ctx.renderOpts.dir) || ''
 
     const globalErrorModulePath = normalizeConventionFilePath(
       dir,
diff --git a/packages/next/src/server/app-render/create-component-tree.tsx b/packages/next/src/server/app-render/create-component-tree.tsx
index 9e1ca07f214e..ee173548df23 100644
--- a/packages/next/src/server/app-render/create-component-tree.tsx
+++ b/packages/next/src/server/app-render/create-component-tree.tsx
@@ -417,9 +417,9 @@ async function createComponentTreeInternal(
     process.env.NODE_ENV === 'development' &&
     ctx.renderOpts.devtoolSegmentExplorer
   const dir =
-    process.env.NEXT_RUNTIME === 'edge'
-      ? process.env.__NEXT_EDGE_PROJECT_DIR!
-      : ctx.renderOpts.dir || ''
+    (process.env.NEXT_RUNTIME === 'edge'
+      ? process.env.__NEXT_EDGE_PROJECT_DIR
+      : ctx.renderOpts.dir) || ''
 
   // Use the same condition to render metadataOutlet as metadata
   const metadataOutlet = StreamingMetadataOutlet ? (
@@ -1139,9 +1139,9 @@ async function createBoundaryConventionElement({
     process.env.NODE_ENV === 'development' &&
     ctx.renderOpts.devtoolSegmentExplorer
   const dir =
-    process.env.NEXT_RUNTIME === 'edge'
-      ? process.env.__NEXT_EDGE_PROJECT_DIR!
-      : ctx.renderOpts.dir || ''
+    (process.env.NEXT_RUNTIME === 'edge'
+      ? process.env.__NEXT_EDGE_PROJECT_DIR
+      : ctx.renderOpts.dir) || ''
   const { SegmentViewNode } = ctx.componentMod
   const element = Component ? (
     <>
diff --git a/packages/next/src/server/app-render/segment-explorer-path.ts b/packages/next/src/server/app-render/segment-explorer-path.ts
index b5f7482eb6e5..852f2204e8a9 100644
--- a/packages/next/src/server/app-render/segment-explorer-path.ts
+++ b/packages/next/src/server/app-render/segment-explorer-path.ts
@@ -9,11 +9,17 @@ export function normalizeConventionFilePath(
   projectDir: string,
   conventionPath: string | undefined
 ) {
+  // Turbopack project path is formed as: "<project root>/<cwd>".
+  // When project root is not the working directory, we can extract the relative project root path.
+  // This is mostly used for running Next.js inside a monorepo.
   const cwd = process.env.NEXT_RUNTIME === 'edge' ? '' : process.cwd()
+  const relativeProjectRoot = projectDir.replace(cwd, '')
 
   let relativePath = (conventionPath || '')
     // remove turbopack [project] prefix
-    .replace(/^\[project\][\\/]/, '')
+    .replace(/^\[project\]/, '')
+    // remove turbopack relative project path, everything after [project] and before the working directory.
+    .replace(relativeProjectRoot, '')
     // remove the project root from the path
     .replace(projectDir, '')
     // remove cwd prefix